Welding is an important process in the manufacture and construction of various products and structures. Applications for welding are widespread and used throughout the world including, for example, the construction and repair of ships, buildings, bridges, vehicles, and pipe lines, to name a few. Welding is performed in a variety of locations, such as in a factory with a fixed welding operation or on site with a portable welder.
In manual or semi-automated welding a user/operator (i.e. welder) directs welding equipment to make a weld. For example, in electric arc welding the welder may manually position a welding rod or welding wire and produce a heat generating arc at a weld location. In this type of welding, the spacing of the electrode from the weld location is related to the arc produced and to the achievement of optimum melting/fusing of the base and welding rod or wire metals. The quality of such a weld is often directly dependent upon the skill of the welder.
The electric welding arc is known to produce ultraviolet (UV) radiation as well as thermal (heat) radiation. The UV radiation produced by the electric welding arc is capable of causing injury comparable to a sun burn. The UV radiation has also been known to cause eye irritation, a condition commonly referred to as “welder's flash” or “arc eye.” The intensity of the UV radiation produced during electric arc welding depends upon many factors such as the process type, welding parameters, electrode and base metal composition, fluxes, and any coating or plating on the base metal. Additionally, tip size, shielding gas, and filler metal composition are among other variables that affect the amount of UV radiation generated. In addition to direct exposure to UV radiation, UV radiation can reflect from surfaces common in a welding environment, such as unpainted metals and concrete floors, resulting in indirect exposure. Further, the effects of UV radiation exposure are cumulative and repeated exposure can result in retinal injury and other health hazards.
The produced thermal (heat) radiation may equally be detrimental to the welder, and excess amounts can be reflective of improper setup of the welding operation, or improper welding technique or a myriad of other technical and/or user-related issues. Therefore, detecting heat exposure, particularly threshold temperatures, is also important in that it may be reflective of the need for a welder to take a break.
UV radiation is commonly divided into three bands, UV-A, UV-B, and UV-C, in order of decreasing wavelength. Natural sunlight is the most prevalent source of UV radiation in all three bands, however UV-C is substantially absorbed by the ozone layer. Generally UV-A has a wavelength from 320 to 380 nanometers; UV-B has a wavelength from 290 to 320 nanometers; and UV-C has a wavelength from 200 to 290 nanometers. The shorter the wavelength the greater the biological effects of the UV radiation. Electric arc welding produces UV radiation in all three bands, but has substantial emissions in the upper end of the UV-C band.
In the past, various methods and devices have been used to shield welders from the UV radiation and/or heat produced by electric arcs. For example, welding helmets, jackets, and gloves are customarily worn that substantially shield the welder from heat or block UV radiation from reaching the welder's eyes and body. In the welding environment, other personnel also commonly wear personal protective equipment such as safety glasses that limit exposure to UV radiation and/or generated heat.
The extent of UV exposure for personnel working around welding arcs varies greatly and is often not precisely known. To limit unintended exposure to nearby persons, curtains and shields of various types have been constructed to isolate the welding operation. The reflection of UV radiation from unpainted metal, concrete, and other surfaces however limits the effectiveness of shielding the welding operation. Welding operations have also been located away from walkways, aisles, and other areas where other personnel are working to reduce exposure to the other personnel, however, this is often impractical when welding operations are conducted in confined areas. Other techniques for avoiding UV exposure have also been employed including placing warning signs around the welding environment highlighting the potential for UV exposure.